A variety of rotary sensors are used to convert the angular position of a rotating object into either analog or digital sensor output. Some examples of rotary sensors include absolute position sensors, incremental position sensors, magnetic sensors, optical sensors, mechanical sensors, various types of encoders, and more. As used herein, the term ‘rotary sensor’ broadly includes any sensing device and related electronics that can be coupled to a rotating object in order to provide a sensor output that is representative of the position, speed, acceleration, and/or any other movement-related characteristic of the rotating object.
Absolute rotary sensors can usually determine the actual rotational position of an object without requiring a home cycle, depending on a history of shaft rotation, or relying on cumulative counts. Typically, absolute rotary sensors divide the entire angular travel of the object into a number of discrete and unique positions; thus, absolute rotary sensors do not lose their position output if there is a loss of power or if the sensor is otherwise powered down.
Incremental rotary sensors, on the other hand, can generally determine the relative position of a rotating object, but usually need to keep a running count of pulses in order to relate the output to some starting or reference point. Some incremental rotary sensors provide two outputs that are 90° out of phase with each other, for example. These types of incremental sensors, sometimes referred to as quadrature encoders, not only indicate the relative position of the rotating object, but also the direction of rotation.
Again, it should be appreciated that the above-mentioned rotary sensors are only examples of some of the types of sensors that could be used to determine the rotational position of an object and that other types, including ones not mentioned here, could also be used in such a capacity.